In the German OEBL-C cellular radio system, radiotelephones are provided which can be tested by the manufacturer using a service card with a dedicated data field. On insertion of the service card into the radiotelephone, the radiotelephone enters a service mode, and test programs are executed. During a service mode the operation of the radiotelephone is tested. For example, range information is tested, the memory is read and/or a test call is performed whereby a service number is called which connects the radiotelephone to a local base station, in response to which the base station transmits a tone signal back to the radiotelephone. With the radiotelephone in a service mode it is not possible for a user to make outgoing calls other than the fixed test call and is not possible to receive incoming calls.
In the GSM pan-European digital cellular radio system, it is intended that subscribers will be issued with smart cards, hereafter referred to as subscriber identity cards, for authorizing subscribers to use the cellular radio system and for identifying the subscriber who is to be billed for the service. Such a system in principal allows a subscriber to use any item of subscriber equipment and to be billed to the same bill irrespective of the equipment used.
An example of an item of GSM subscriber equipment is a mobile radiotelephone which is enabled for use on insertion of a subscriber identity card. A subscriber validation code, which is unique for each user, is permanently programmed into a memory of the card, whereby on insertion of the card into the radio the validation code is read from the card and transmitted to a base station local to the radio. The base station then checks the validation code and sends a signal back to the radio so as to enable the radio for operation. Once enabled the radiotelephone can provide all the call functions which are available with the radiotelephone, which will depend on its type. The call functions may include, for example, incoming and outgoing calls, international calls, abbreviated dialling using preprogrammed numbers stored in a memory internal to the telephone, use of a telephone answering machine service, and use of data equipment such as fax machines. Such functions are well known in the art.
A subscriber on the GSM system can subscribe to one of a number of levels of subscription. The full service may be subscribed for, which means that the subscriber may make calls anywhere within the European-wide area covered by the service and may make international calls. Alternatively a national-call only service may be subscribed for which means that calls may only be made from within a home nation to within the same nation.
Other levels of service may be offered by a service operator. The level of service is identified within the system, rather than at the subscriber equipment. I.e. when a subscriber attempts to make a call and his subscriber ID is transmitted to a base station, a check is made at the base station or its local controller to determine whether the subscriber is authorized to make the call which is being attempted. If he is not authorized, e.g. through having subscribed for a more limited service (or through non-payment of bill or otherwise), no authorization signal is transmitted back to the subscriber unit and no handshake occurs.
In the GSM specification Recommendation 02.07 version 3.1.0 of 15 Apr. 1989, a fixed number call feature is described whereby, by use of an electronic lock, it is possible to place a bar on calling any numbers other than those preprogrammed in the mobile station. The service described has two sub-categories: all calls are made to only one predetermined number, or calls may be made to several predetermined numbers, the required number being selected by means of an abbreviated address code. In both cases, the actual directory number is transmitted on the radio path. These features are implemented in the mobile unit (rather than the card). A suitable electronic lock would be a number to be entered in the keypad. It is also possible to provide a group call facility whereby the GSM mobile operates like a private exchange. This is implemented at the switch.
FIG. 1 shows the organization of the memory fields of a GSM Subscriber Identity Module (smart card). In this figure a root directory 10 is shown at memory location #3F00. Through this directory, access can be gained to card-holder data field 11, administrative data field 12 and SIM identification data field 13 and to a GSM directory 14 and a telecom directory 15. The data fields 11, 12 and 13 are for administration purposes for the benefit of the system operator.
GSM directory 14 gives access to 8 further data fields 16 to 23. Field 16 gives the SIM serial number, field 17 (IMSI) gives the identification number identifying the subscriber, field 18 (KI) gives a key for the authentication algorithm, field 19 (TMSI) gives a temporary registration number which is a substitute for the IMSI and gives a number (LAI) identifying the current cell. Field 20 gives a key (Kc) for encryption of speech and gives a ciphering key sequence number (n). Field 21 gives the operator identifier (PLMN), which also identifies the country, field 22 gives details of a broadcasting channel (PCTH) to which the mobile locks, eg frequency details thereof, and field 23 provides information on the initial channel accessed, for traffic control purposes.
Root directory 10 also gives access to a telecom directory 15. From the user's point of view, the contents of this directory are of greatest interest. Field 24 contains abbreviated dial telephone numbers, field 25 gives call set up information for the purposes of abbreviated dialling. Field 25 identifies whether the call is regular speech or, if it is a data call, it identifies the baud rate, package switching format etc. Field 26 is available for storing up to five predefined or received messages, to a maximum of 180 characters. Field 27 contains predetermined numbers for dialling, and when the user has blocked outgoing calls, only these numbers can be dialled. Field 28 counts charge pulses for the purposes of billing.
The above described systems do not allow a subscriber to control the manner in which his subscriber card may be used, beyond the limited choice of levels of service available from the service operator.